Troost on the Pyroxene. 
55 
9. Suhtractive P. * The Bisunitary, or the preceding, 
having the sharp angle of the summit replaced by a tri- 
angular face, being sometimes undulated or curvilinear. 
10. Jimbiguous P.t The former, in which the triangu^- 
lar face is so much enlarged as to make the two faces of the 
summit disappear. 
11. Dioctsedral P.J The variety Triunitary^ having the 
edges of the terminal faces emarginated. 
12. Epimeridal P. || An eight sided prism, with a sum- 
mit with five faces. This is the form of the white Py- 
roxene of the United States. 
13. Octo-duo decimal P.§ An eight sided prism, with a 
summit of eight faces. 
14. Trioctonal P. IT An eight sided prism, with a sum- 
mit of eight faces — from Connecticut, United States. 
15. Stenomonal P.** Eight sided prism, with summits 
of eight faces, 
16. OctO'Vigesimal V A\ An eight sided prism, having 
* Traite, fig. 142. f Mem. Mus. 1, p. 284, fig. 27. 
T Traite 3, p. 85, fig. 143. 
11 Annal. Mus. vol. xix. p. 257 — vol. xiv. fig. 1. 
§ Annal. Mus. vol. ix. et Jour. Min. vol. xxiii. p. 152, pi. 3, fig. 5. 
% Jour. Min. vol. xxiii. p. 152, pi. 3, fig. 6. 
** Mus. 1, p. 289, pi. 14, figs. 31, 32. The varieties Epimeridal Sind 
Stenomonal show the truth of the Remarks of Mr. Hauy regarding the 
var. Odo-vigesimalf in the Jour, the Museum. — This crystal offers a re- 
markable instance of those whims of crystallization happening in con- 
sequence of certain faces being more or less distant from the centre — 
the deviation originating in some of the faces having increased in size 
at the expense of others, which change the entire aspect or physiogno- 
my of the crystal, so that it is with difficulty that we recognize the sam^ 
type of the crystal. 
ft Annal. Mus. vol. ix. et Mem, Mus. 1, p. 290, pL 14, fig. 33. 
4 
